a. Field of the Invention
The present disclosure pertains generally to an electrophysiological device and method for providing energy to biological tissue and, more particularly, to a family or group of ablation systems that employ a form of vacuum stabilization to provide greater contact between at least one ablation element and a targeted volume of tissue.
b. Background Art
Ablation of a volume of target tissue can involve moving and non-moving organs such as a kidney or liver and a heart, respectively. In the latter case, the heart beats or contracts when an electrical impulse originating from the sinoatrial node (SA node) travels through the right and left atria, and then activates the atrioventricular node (AV node). From the AV node, the electrical impulse travels through the right and left ventricles via a group of specialized fibers called the His-Purkinje fibers. The impulse causes synchronized contraction of the chambers of the heart. Cardiac conduction irregularities, or any change from the normal sequence of electrical impulses, can cause various arrhythmias, such as atrial fibrillation, atrial flutter and certain ventricular arrhythmias. These conditions can decrease cardiac output and reduce tissue perfusion to the detriment of a subject.
Cardiac ablation is a procedure for treating various arrhythmias by selectively damaging heart tissue in the region where aberrant or abnormal electrical activity is occurring. The damaged tissue blocks the aberrant pathways and restores normal heart rhythm. Various energy delivery schemes may be used, including, but not limited to, cryogenic ablation, radiofrequency (RF) ablation, laser ablation, ultrasound ablation, and microwave ablation. Ablation devices are used to create linear lesions or tiny scars that cut-off or disconnect the abnormal electrical pathway.
Ablation procedures rely on stable contact between the medical device and the targeted tissue. For certain ablation procedures involving the cardiac anatomy, such as a left atrial pulmonary vein isolation (PVI) procedure, the epicardial surfaces of posterior portions of a heart must be accessed. To reach such surfaces from an anterior location (e.g., via a minimally invasive subxiphoid incision) requires the catheter, in particular the distal portion of an elongate catheter, to traverse a tortuous route to reach target tissue. Establishing adequate contact with the target tissue to successfully perform a PVI (i.e., create a continuous lesion or set of connected lesions around one or more pulmonary veins) presents challenges to the practitioner. Furthermore, in some transvenous catheter applications, the point of electrode-tissue contact is as far as about 150 cm away from the point of application of force. These challenges give rise to functional and theoretical challenges associated with conventional devices, and thus, the ability to accurately stabilize the device at the point of contact with a line of target tissue is increasingly important. The use of reduced pressure, for example by applying a vacuum at or near the point of contact between the medical device and the target tissue, has been contemplated for adhering the device to tissue.
There is a need for electrophysiological devices that provide greater contact stability for control of medical treatments involving contact with a volume of targeted tissue.
There is a need for improved ablation elements that provide greater stability, i.e., limit relative motion between the ablating element and the tissue at the point of contact.